I propose to use a combination of genetic, biochemical and morphological methods to determine the mechanisms by which organelles move through cells. It is important to understand these mechanisms because such physiologically important phenomena as axonal transport and enzyme and hormonal secretion are forms of organellar translocation. I propose to study the mechanisms of organellar translocation in the filamentous fungus Aspergillus nidulans which is uniquely suited for combined genetic, morphological and biochemical studies of these phenomena. Initially I propose to isolate conditionally-lethal mutants and screen these mutants for blockage of nuclear and mitochondrial migration under restrictive conditions. In addition to randomly isolated conditionally-lethal mutants, I propose to isolate conditionally-lethal suppressors of existing conditionally-lethal tubulin mutants, suppressors of existing and newly-isolated organellar translocation mutants and conditionally-lethal cytochalasin-resistant mutants. Previous experience suggests that organellar translocation mutants should occur at a high frequency among these mutants. The newly-isolated organellar translocation mutants will be tested for allelism to existing organellar translocation mutants and to each other and will be mapped to locus. These mutants will be characterized morphologically at the light-microscopic level to determine if each mutation specifically blocks one form of organellar translocation, such as nuclear movement, or if it has more general effects. These mutants will be examined in the electron microscope to determine if they affect microtubule assembly or distribution. Finally, I will attempt to identify the defective gene products by two-dimensional gel electrophoresis and I will attempt to develop microinjection and DNA transformation assays for the defective gene products.